The electronic and photographic or photolithographic industries have historically employed organic solvents, acids, and salts. With increasing demands for decreased use of toxic chemicals including a variety of organic products, research in virtually all organic chemical based industries has shifted focus to the development of more environmentally compatible alternatives to organic chemicals. In the electronics, and photographic or photolithographic industries, few alternatives have been provided for the typically organic components of photoresists. In particular, there is a need in the art for environmentally compatible photoinitiators useful in photoresists.
Photoinitiators are known in the art, and typically include compounds whose chemical composition is altered upon exposure to radiation. Examples of well known photoactive agents include sulfonium and iodonium salts, such as those described in U.S. Pat. Nos. 4,407,759, 4,417,061, and 4,537,854 all to Crivello; and J. M. J. Frechet, Pure and Applied Chemistry 63(9):1239 (1992). More recently, Sakamizu, et al., Polymeric Materials Science and Engineering, American Chemical Society 72:199 (1995), discussed tri(alkylsulfonyloxy)benzene salts as one class of water-soluble onium salt photoacid generators. There remains a need in the art for alternative photoinitiators which are useful in photoresist compositions, and environmentally compatible. In addition, there remains a need in the art for photoinitiators which are water-soluble.